There exists an ever increasing need and demand for efficient, effective and economical gravity feed display systems which provide maximum flexibility to a merchant in the areas of conserving floor and/or shelf space, minimizing assembly time, and maximizing the storage and display of saleable goods on such assemblies. Many different types of gravity feed devices and systems have been designed and manufactured for use in a multitude of applications for merchandising shelved products to consumers. Such known gravity feed devices teach a wide variety of constructions including modular constructions which permit the vertical stacking of one shelf unit upon the other as well as other types of multi-tiered and multiple shelf constructions. Such known prior art constructions are for the most part characterized by complicated and cumbersome mechanisms which are inconvenient, awkward and difficult to handle and include multiple component parts and complicated support frame structures as well as complicated interconnection means. Many of the known modular type display devices typically support the shelf members or floor display areas associated therewith in a horizontal position only and such units have no capability or adaptability for orienting such shelf or floor areas so as to achieve a gravity feed operation. See for examples the constructions shown in U.S. Pat. Nos. 4,564,111; 4,574,709; 4,593,826; 4,618,115; and 4,621,740. Other known shelving units which afford a gravity feed operation utilize various mechanisms for tilting or inclining the shelf members associated therewith so as to accomplish the same. See for examples the constructions shown in U.S. Pat. Nos. 4,531,646 and 4,627,542. Still other known gravity feed constructions utilize a special bracket design for achieving the multi-tiered gravity feed arrangement such as U.S. Pat. No. 4,593,823 which discloses a two-tier gravity feed system.
Nathan et al U.S. Pat. No. 4,550,838, although disclosing a multi-tiered gravity feed shelf arrangement, likewise suffers from certain disadvantages and shortcomings. For example, the modular display device of Nathan et al utilizes column-like dowels which are engageable with upper and lower recesses located wholly within the side retaining walls associated with each respective shelf member for vertically assembling the respective shelf members in a gravity feed orientation. The size and shape of the upright support members are therefore controlled and limited by the size and shape of the side walls associated with each respective shelf member. The front wall portion of each shelf member associated with the Nathan et al device is specifically designed to include a support edge which lies at an acute angle with the underside portion of each shelf member, which support edge provides a support means for the shelf member when such shelf member is used as the lowermost base shelf member and is disposed in its inclined display position. When assembled, the column-like support dowels are not vertically oriented with respect to the horizontal support surface upon which the overall display unit is positioned, but instead, the support dowels are inclined rearwardly towards the back portion of the unit. This arrangement is not very stable, particularly when a plurality of such shelf members are vertically stackably arranged one above the other, and such an arrangement is also subject to considerable racking. This is not true of the present constructions as will be hereinafter explained. The present shelving units as well as the improved means for vertically stacking such units in spaced relationship one above the other in a gravity feed orientation is clearly different from and distinguishable over the above known prior art constructions including the Nathan et al construction. None of the known gravity feed systems discloses a simple, efficient, and cost effective means for achieving a gravity feed merchandising array whereby the individual shelf members are automatically supported in a stable inclined position. Also, none of the known prior art devices provides means for converting existing modular type display units having a plurality of substantially flat horizontal display areas associated therewith to gravity feed systems as is true of the various shelf conversion means associated with the present invention.